Tropical Storm ISAAC (Text)

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TROPICAL STORM ISAAC DISCUSSION NUMBER 22
NWS NATIONAL HURRICANE CENTER MIAMI FL AL092012
1100 AM EDT SUN AUG 26 2012
VISIBLE SATELLITE AND IMAGERY SUGGEST THAT THE TROPICAL CYCLONE IS
GRADUALLY BECOMING BETTER ORGANIZED. THERE ARE INDICATIONS OF
INNER CORE DEVELOPMENT WITH INCREASED CONVECTION NEAR AND OVER THE
CENTER...AND A PARTIAL EYEWALL IS IN EVIDENCE ON RADAR IMAGERY. THE
BANDING FEATURES HAVE BECOME MORE DISTINCT OVER THE NORTHERN AND
EASTERN SEMICIRCLES OF THE CIRCULATION. THE CURRENT INTENSITY
ESTIMATE IS HELD AT 55 KT PENDING OBSERVATIONS FROM AN AIR FORCE
HURRICANE HUNTER AIRCRAFT THAT SHOULD BE IN THE CENTER SHORTLY.
ISAAC CONTINUES TO EXHIBIT A WELL-DEFINED UPPER-LEVEL OUTFLOW
PATTERN...AND GRADUAL STRENGTHENING IS LIKELY AS THE CYCLONE
TRAVERSES THE EASTERN GULF OF MEXICO OVER THE NEXT COUPLE OF DAYS.
THE OFFICIAL WIND SPEED FORECAST IS SIMILAR TO THE PREVIOUS NHC
FORECAST AND IS ALSO CLOSE TO THE LATEST STATISTICAL-DYNAMICAL
GUIDANCE.
THE TRACK FORECAST BEYOND DAY 2 HAS BECOME PROBLEMATIC. DYNAMICAL
MODELS DEPICT THE CYCLONE MOVING INTO A BREAK IN THE SUBTROPICAL
RIDGE NORTH OF THE GULF COAST IN ABOUT 72 HOURS. HOWEVER THERE IS
A LARGE SPREAD AMONG THE MORE RELIABLE TRACK MODELS. FOR EXAMPLE...
THE ECMWF FORECAST IS ABOUT 300 N MI EAST OF THE GFS SOLUTION AT DAY
3. SINCE THE DYNAMICAL MODEL CONSENSUS HAS SHIFTED WESTWARD...THE
OFFICIAL TRACK FORECAST IS MOVED A BIT TO THE WEST OF THE PREVIOUS
ONE. THIS REQUIRES AN EXTENSION OF THE HURRICANE WATCH WESTWARD
ALONG THE LOUISIANA COAST. IT SHOULD BE NOTED THAT THERE IS
GREATER THAN USUAL UNCERTAINTY IN THE TRACK FORECAST.
THROUGHOUT THE PERIOD...IT IS IMPORTANT NOT TO FOCUS ON THE EXACT
FORECAST TRACK SINCE SIGNIFICANT HAZARDS EXTEND WELL AWAY FROM THE
CENTER.
FORECAST POSITIONS AND MAX WINDS
INIT 26/1500Z 23.9N 80.8W 55 KT 65 MPH
12H 27/0000Z 25.0N 82.7W 65 KT 75 MPH
24H 27/1200Z 26.1N 84.8W 70 KT 80 MPH
36H 28/0000Z 27.4N 86.4W 75 KT 85 MPH
48H 28/1200Z 28.5N 87.6W 80 KT 90 MPH
72H 29/1200Z 30.5N 89.0W 90 KT 105 MPH
96H 30/1200Z 32.5N 89.5W 30 KT 35 MPH...INLAND
120H 31/1200Z 34.5N 89.5W 20 KT 25 MPH...INLAND
$$
FORECASTER PASCH/ROBERTS
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